Runoff under sprinkler irrigation systems causes soil erosion and reduces water infiltration uniformity.
Previous studies have shown that applying polyacrylamide (PAM) with irrigation water can reduce runoff and soil loss.
We hypothesized that applying PAM with three consecutive irrigations would more effectively control runoff and erosion
than applying the same total amount of PAM with a single irrigation. This study was conducted in the laboratory with a
Rad silt loam (coarse silty, mixed, superactive mesic Durinodic Xeric Haplocambid) at 6.5% slope. Water was applied at
80 mm h- 1 (3.2 in. h-1 ) for 10 min [13 mm (0.5 in.) application depth] for four irrigations. PAM was applied at 3 kg ha-1
(2.7 lb a-1 ) with irrigation water during the initial irrigation (single) or at 1 kg ha- 1 (0.9 lb a-1 ) during the first three
irrigations (multiple). Both multiple and single PAM treatments caused significantly less runoff than the control for all
four irrigations. However, the multiple PAM treatment reduced runoff approximately 30% more than the single
application during the last two irrigations. Applying PAM at 3 kg ha-1 (2.7 lb a-1 ) with one irrigation reduced cumulative
soil loss by 60% compared to the control. Applying PAM at the same rate in three consecutive irrigations reduced
cumulative soil loss by 80%. Both single and multiple PAM applications reduced runoff and soil loss, but multiple
applications more effectively controlled runoff longer than a single application

Aase, J.K.

Bjorneberg, D.L.

Northwest Irrigation & Soils Research Laboratory Publications

Multiple polyacrylamide applications for controlling sprinkler irrigation runoff and erosion

USDA - ARS - NWISRL

\02.6MULTIPLE POLYACRYLAMIDE APPLICATIONS FOR CONTROLLINGSPRINKLER IRRIGATION RUNOFF AND EROSIOND. L. Bjorneberg, J. K. AaseABSTRACT. Runoff under sprinkler irrigation systems causes soil erosion and reduces water infiltration uniformity.Previous studies have shown that applying polyacrylamide (PAM) with irrigation water can reduce runoff and soil loss.We hypothesized that applying PAM with three consecutive irrigations would more effectively control runoff and erosionthan applying the same total amount of PAM with a single irrigation. This study was conducted in the laboratory with aRad silt loam (coarse silty, mixed, superactive mesic Durinodic Xeric Haplocambid) at 6.5% slope. Water was applied at80 mm h- 1 (3.2 in. h-1 ) for 10 min [13 mm (0.5 in.) application depth] for four irrigations. PAM was applied at 3 kg ha- 1(2.7 lb a-1 ) with irrigation water during the initial irrigation (single) or at 1 kg ha- 1 (0.9 lb a-1) during the first threeirrigations (multiple). Both multiple and single PAM treatments caused significantly less runoff than the control for allfour irrigations. However, the multiple PAM treatment reduced runoff approximately 30% more than the singleapplication during the last two irrigations. Applying PAM at 3 kg ha- 1 (2.7 lb a-1 ) with one irrigation reduced cumulativesoil loss by 60% compared to the control. Applying PAM at the same rate in three consecutive irrigations reducedcumulative soil loss by 80%. Both single and multiple PAM applications reduced runoff and soil loss, but multipleapplications more effectively controlled runoff longer than a single application.Keywords. Runoff Soil erosion, Polyacrylamide, Sprinkler irrigation.Center pivots irrigate about one-third of theirrigated land in the United States (USDA, 1998).These systems are popular because theyuniformly apply water with little labor and can beused on land unsuitable for surface irrigation. However,runoff can be a problem because the water application rateoften exceeds the soil infiltration rate (Gilley and Mielke,1980; Kincaid et al., 1969). Runoff on a center pivot-irrigated field generally does not flow from the field, butponds and infiltrates in low areas within the field, resultingin reduced irrigation uniformity.Several laboratory studies have shown that sprayingconcentrated PAM solutions [500 mg L- 1 (0.05%)] on thesoil surface at rates equal to or greater than 20 kg ha- 1(18 lb a- 1 ) increased final infiltration rate and decreasedsoil erosion during simulated rainfall (Ben-Hur and Keren,1997; Levy and Agassi, 1995; Levin et al., 1991; Smith etal., 1990). Spraying PAM directly on the soil, however,requires a large volume of solution (i.e., > 5000 L ha- 1 or530 gal a- 1 ) or a high viscosity solution. Conversely,applying PAM with irrigation water generally requires lessArticle was submitted for publication in March 2000; reviewed andapproved for publication by the Soil & Water Division of ASAE in July2000.Mention of a trade name, proprietary product, or specific equipmentdoes not constitute a guarantee or warranty by the USDA and does notimply approval of a product to the exclusion of others that may besuitable.The authors are David L. Bjorneberg, ASAE Member Engineer,Agricultural Engineer, and J. Kristian Aase, Soil Scientist, USDAAgricultural Research Service, Northwest Irrigation and Soils ResearchLaboratory, Kimberly, Idaho. Corresponding author: David L.Bjorneberg, Northwest Irrigation and Soils Research Laboratory, 3793 N3600E, Kimberly, ID 83341-5076, phone: 208.423.6521, fax:208.423.6555, e-mail<bdavid@kimberly.ars.pn.usbr.gov >.PAM and is more effective than applying PAM directly tothe soil. Ben-Hur et al. (1989) found thai applying 5 kgPAM ha- 1 (4.5 lb a- 1 ) with water during lab simulationsmore effectively prevented crust formation than sprayingan equivalent amount of PAM on the soil surface. ApplyingPAM at 10 mg L- 1 with simulated rainfall increased finalinfiltration rate compared to an untreated control, whileapplying 20 kg PAM ha- 1 (18 lb a- 1 ) directly to the soil didnot (Flanagan et al., 1997). Levy et al. (1992) applied threePAM rates [3, 6, and 12 kg ha- 1 (2.7, 5.4, and 11 lb a- 1 )]with irrigation water for three consecutive irrigations onsmall trays in the laboratory. They noted that PAMincreased final infiltration rate during treated irrigations,but final infiltration rates decreased to values similar tountreated soil after irrigating twice with only water.Similarly, Aase et al. (1998) showed that applying 2 kgPAM ha- 1 (1.8 lb a- 1 ) with irrigation water in a laboratorystudy reduced runoff 70% compared to the control.Reducing runoff also reduced soil loss by 75% compared tothe control. However, the single PAM application, even at6 kg PAM ha- 1 (5.4 lb a- 1 ) , had little effect on runoff aftertwo subsequent irrigations with only water. Wehypothesized that applying PAM with three consecutiveirrigations would more effectively control runoff anderosion than applying the same total amount of PAM with asingle irrigation. Therefore, the objective of this study wasto compare single and multiple PAM application effects onrunoff and soil loss using laboratory sprinkler irrigationsimulations.MATERIALS AND METHODSLaboratory equipment and procedures used during thisstudy were similar to those used by Aase et al. (1998) tocompare runoff and soil loss from soil treated with 0, 1, 2,Applied Engineering in AgricultureVOL. 16(5): 501-504	2000 American Society of Agricultural Engineers 	 5014 or 6 kg PAM ha- 1 (0, 0.9, 1.8, 3.6 or 5.4 lb a- 1 ) during asingle irrigation. Soil was irrigated with an oscillatingnozzle simulator similar to one described by Meyer andHarmon (1979). An 8070 Veejet nozzle, 3 m (10 ft) abovethe soil surface, applied water at 80 mm h- 1 (3.2 in. h- 1 )with a nozzle pressure of 76 kPa (11 psi). Irrigations lasted10 min and applied 13 mm (0.5 in.) of water. Thisapplication rate and depth were similar to those on theouter spans of center pivots in southern Idaho. Theresulting droplet energy from this type of nozzle sprayingdownward was about 25 J kg- 1 , calculated according toKincaid (1996).We used well water for all tests. The water had anelectrical conductivity (EC) of 0.73 dS m- 1 , sodiumadsorption ratio (SAR) of 1.7, and pH of 7.2. PAM-treatedirrigation water was mixed by adding a concentrated PAMsolution [1920 mg L- 1 active ingredient (0.19%)] to wellwater in 210-L (55-gal) containers to achieve the desiredPAM concentration. The concentrated PAM solution wasprepared from a dry granular material with molecularweight of 12 to 15 Mg mole- 1 and an 18% negative chargedensity (Superfloc A836, marketed by American CyanamidCo., Roanoke, Texas). All PAM rates and concentrationsreported in this article are active ingredient, not bulkmaterial.We used a Rad silt loam (coarse silty, mixed,superactive mesic Durinodic Xeric Haplocambid) for thisstudy. Soil texture, determined by hydrometer method, was30% clay, 55% silt, and 15% sand (silty clay loam). Thesoil had 18 g kg- 1 (1.8%) organic matter, saturated pastepH of 7.6, saturated paste extract EC of 1.0 dS m- 1 , andSAR of 1.1. Soil was passed through a 6.4-mm (0.25-in.)screen prior to filling the steel boxes. The boxes were1.2 m (4 ft) wide, 1.5 m (5 ft) long, and 0.2 m (8 in.) deep,except on the downslope end which was 0.15 m (6 in.)deep so the runoff trough could be attached. To avoidlayering and segregation, the soil surface was stirred andmixed prior to leveling. This resulted in a uniform 0.15 m(6 in.) soil depth in the entire box with lightly packedsurface. The resultant bulk density was about 1.0 Mg m- 3(62 lb ft-3 ), similar to freshly tilled surface soil. Soilsurface slope was set at 6.5% to represent a steep portion ofa field where runoff would be a problem.Three treatments, control, single PAM application, andmultiple PAM applications, were compared. Each treatmentwas irrigated four times. The elapsed time betweenirrigations was 7 to 10 days, enough time for the soilsurface to dry. PAM application rate was chosen based onthe previous study by Aase et al. (1998). The singleapplication treatment received 3 kg PAM ha- 1 (2.7 lb a- 1 )at 22.5 mg PAM L- 1 with the first irrigation, followed bythree water-only irrigations. The multiple applicationtreatment received 1 kg PAM ha- 1 (0.9 lb a- 1 ) at 7.5 mgPAM L- 1 during the first three irrigations, followed by afourth irrigation with only water. The control treatment wasirrigated with only water for all four irrigations. All runofffrom a soil box during an irrigation was collected in acontainer via the runoff trough affixed to the down-slopeend of the box. Collected runoff was weighed and laterfiltered to determine sediment mass.Prior to each irrigation, we collected two, 19-mm (0.75-in.) diameter soil cores from each soil box to determineantecedent water content. One core was taken from thedown-slope end of the box and the other from the up-slopeend. Soil cores were divided into 0 to 75 mm (0 to 3 in.)and 75 to 150 mm (3 to 6 in.) depths. After the fourthirrigation, we collected surface soil about 5 mm (0.2 in.)deep for wet aggregate stability analysis. Samples werelifted from the soil surface with spatulas, sealed in plasticbags, and refrigerated until analysis according to theprocedure described by Kemper and Rosenau (1986) asmodified by Lehrsch et al. (1991).Each treatment was replicated six times. Data wereanalyzed as a randomized complete block. Significanttreatment differences were identified using Duncan'smultiple range test (P < 0.05).RESULTS AND DISCUSSIONRunoff from these laboratory boxes represents runofffrom steep areas near the outer portion of a center pivot-irrigated field and not runoff from an entire field. A single3 kg PAM ha- 1 (2.7 lb a- 1 ) application eliminated runofffor the first irrigation and significantly reduced runoffcompared to the control for the three remaining irrigations(fig. 1). Multiple PAM applications also significantlyreduced runoff for all four irrigations. Runoff was notsignificantly different between the single and multiplePAM treatments for the first two irrigations. However, themultiple application treatment reduced runoff an additional30% for irrigations 3 and 4 compared to the singleapplication. Multiple PAM applications reducedcumulative runoff 50% compared to the control. Thirty-four percent [18 mm (0.7 in.)] of the total water appliedduring the four irrigations ran off the control treatmentcompared to just 23% [12 mm (0.5 in.)] for the singleapplication and 17% [9 mm (0.35 in.)] for the multipleapplication.Both PAM application techniques significantly reducedsoil loss for all irrigations (fig. 2). Although the multiplePAM treatment had less runoff than the single applicationfor irrigations 3 and 4, soil loss was not significantlydifferent between the two PAM treatments for any of the654EE0 3202	 3	4Irrigation NumberFigure 1-Mean runoff from each of the four irrigations by treatment.PAM was applied with irrigation 1 for the single treatment andirrigations 1-3 for the multiple treatment. Columns with the sameletter within an irrigation are not significantly different at P < 0.05.502	APPLIED ENGINEERING IN AGRICULTURE2000) 600 -400 -1800 	1600 -1400 -1.3 1200 -cr,1000800 -baaaaCI controln single0 multiple42	 3Irrigation Number35aa-a, 20 -a)E a'a 15-rn)a)c2 10-5CI control• single0 multiple2	 3	 4Irrigation NumberFigure 2–Mean soil loss from each of the four irrigations bytreatment. PAM was applied with irrigation 1 for the single treatmentand irrigations 1-3 for the multiple treatment. Columns with thesame letter within an irrigation are not significantly different at P <0.05.four irrigations. Runoff sediment concentration was notsignificantly different between the two PAM treatments orbetween the control and the single application. However,the multiple PAM treatment had significantly lowersediment concentration than the control for all irrigations(fig. 3). Cumulative soil loss over the four irrigations was1.5 Mg ha- 1 (0.68 ton a- 1 ) and 0.69 Mg ha- 1 (0.31 ton a- 1 )for the single and multiple PAM treatments, respectively.This was 60 and 80% less than the cumulative soil loss forthe control [3.8 Mg ha- 1 (1.7 ton a- 1 )].Surface soil water content was not different amongtreatments before each irrigation. Applying PAM withirrigation water significantly increased aggregate stability,measured after the fourth irrigation, compared to theuntreated soil. Aggregate stability was not significantlydifferent between the two PAM application techniques,following a similar trend as soil loss. The single andmultiple PAM treatments averaged 80% and 85% stableaggregates, respectively, compared to 66% stableaggregates for the control.Runoff increased with each irrigation for the singlePAM application, but remained almost constant after thefirst irrigation for the multiple application (fig. 1). Soilloss, however, increased with each irrigation for alltreatments (fig. 2). PAM could stabilize the soil surfaceduring three consecutive irrigations for the multipleapplication treatment, but the PAM-stabilized surface wasprobably degraded gradually by erosion and water dropletimpact with each consecutive irrigation on the singletreatment. Multiple PAM applications may have enhancedinfiltration by preserving pore structure (Sojka et al.,1998), but did not significantly reduce soil detachment bywater droplets and therefore did not reduce soil erosioncompared to the single application treatment.CONCLUSIONSApplying 1 kg PAM ha- 1 (0.9 lb a- 1 ) with threeconsecutive simulated irrigations reduced runoff more thanapplying the same total amount of PAM with oneirrigation. Soil loss, however, was similar between the twoPAM application techniques, and both had less soil lossthan the control. Results from this study indicate that PAMmore effectively controls runoff from sprinkler irrigationwhen applied with multiple irrigations than when appliedwith a single irrigation. Keep in mind that we applied< 10% of seasonal water need for many crops. AdditionalPAM applications may be needed for season-long benefits.Given the cost of PAM ($13-17 kg- 1 or $6-8 lb- 1 ),practices such as conservation tillage or reservoir tillagemay be more cost effective than applying PAM. Innovativeapplication techniques allowing PAM to be applied only toouter spans of a center pivot may improve the feasibility ofapplying PAM with sprinkler irrigation.Figure 3–Average sediment concentration in runoff from each of fourirrigations by treatment. * No runoff occurred from any replicationof the single treatment and two replications of the multiple treatmentduring irrigation 1. Therefore statistical analysis was not conductedfor irrigation 1. Columns with the same letter within an irrigation arenot significantly different at P < 0.05.REFERENCESAase, J. K., D. L. Bjomeberg, and R. E. Sojka. 1998. Sprinklerirrigation runoff and erosion control with polyacrylamide-Laboratory tests. Soil Sci. Soc. Am. J. 62(6): 1681-1687.Ben-Hur, M., and R. Keren. 1997. Polymer effects on waterinfiltration and soil aggregation. Soil Sci. Soc. Am. J. 61(2):565-570.Ben-Hur, M., J. Fans, M. Malik, and J. Letey. 1989. Polymers assoil conditioners under consecutive irrigations and rainfall. SoilSci. Soc. Am. J. 53(4): 1173-1177.Flanagan, D. C., L. D. Norton, and I. Shainberg. 1997. Effect ofwater chemistry and soil amendents on a silt loam soil—Part 1:Infiltration and runoff. Transactions of the ASAE 40(6): 1549-1554.Gilley, J. R., and L. N. Mielke. 1980. Conserving energy with low-pressure center pivots. J. Irrig. Drain. Div. ASCE 106(IR1): 49-59.Kemper, W. D., and R. C. Rosenau. 1986. 2nd Ed. Aggregatestability and size distribution. In Methods of Soil Analysis:Physical and Mineralogical Methods, Part 1, ed. A. Klute, 425-442. Madison, Wis.: ASA.Kincaid, D. C. 1996. Spraydrop kinetic energy from irrigationsprinklers. Transactions of the ASAE 39(3): 847-853.VOL. 16(5): 501-504	503Kincaid, D. C., D. F. Heermann, and E. G. Kruse. 1969.Application rates and runoff in center-pivot sprinkler irrigation.Transactions of the ASAE 12(6): 790-794, 797.Lehrsch, G. A., R. E. Sojka, D. L. Carter, and P. M. Jolley. 1991.Freezing effects on aggregate stability affected by texture,mineralogy, and organic matter. Soil Sci. Soc. Am. J. 55(5):1401-1406.Levin, J., M. Ben-Hur, M. Gal, and G. J. Levy. 1991. Rain energyand soil amendments effects on infiltration and erosion of threedifferent soil types. Aust. J. Soil Res. 29(3): 455-465.Levy, G. J., J. Levin, M. Gal, M. Ben-Hur, and I. Shainberg. 1992.Polymers' effects on infiltration and soil erosion duringconsecutive simulated sprinkler irrigations. Soil Sci. Soc. Am. J.56(3): 902-907.Levy, G. J., and M. Agassi. 1995. Polymer molecular weight anddegree of drying effects on infiltration and erosion of threedifferent soils. Australian J. Soil Res. 33(6): 1007-1018.Meyer, L. D., and W. C. Harmon. 1979. Multiple-intensity rainfallsimulator for erosion research on row sideslopes. Transactionsof the ASAE 22(1): 100-103.Smith, H. J. C., G. J. Levy, and I Shainberg. 1990. Water-dropletenergy and soil amendments: Effect on infiltration and erosion.Soil Sci. Soc. Am. J. 54(4): 1084-1087.Sojka, R. E., R. D. Lentz, and D. T. Westermann. 1998. Water anderosion management with multiple applications ofpolyacrylamide in furrow irrigation. Soil Sci. Soc. Am. J. 62(6):1672-1680.USDA. 1998. 1998 Farm and Ranch Irrigation Surve y. NationalAgricultural Statistics Service. http://www.nass.usda.gov/census/.504	APPLIED ENGINEERING IN AGRICULTURE

https://eprints.nwisrl.ars.usda.gov/id/eprint/109/1/1020.pdf

Multiple polyacrylamide applications for controlling sprinkler irrigation runoff and erosion

Abstract

Similar works

Full text

Available Versions

Northwest Irrigation & Soils Research Laboratory Publications

USDA - ARS - NWISRL